In a decomposition of CRNs due to Horn and
Jackson [1]} and
Feinberg [2]}, the sets of particles either
removed or red created are called complexes.
We denote the complexes that appear in a CRN with subscripts \(i\) , \(j\) ;
each reaction corresponds to a unique ordered pair \(\left( ji \right)\) 
that removes complex \(i\)  and adds complex \(j\) .
